個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另外，由電池(chi)提(ti)供的安全信號指(zhi)示電池(chi)是(shi)否呈(cheng)現在系(xi)統(tong)中(zhong)和(he)是(shi)否有熱引起的告警或在其他(ta)系(xi)統(tong)失(shi)效時是(shi)否電池(chi)失(shi)效。SBS顯著特點是(shi)安全、使用容易和(he)兼容性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太(tai)熱，則充電(dian)也將終止(zhi)。

　　SMBus 為系(xi)統(tong)和電(dian)源管理這樣的(de)(de)任務(wu)提(ti)供了一(yi)條(tiao)控(kong)(kong)制(zhi)總線，使(shi)(shi)用(yong) SMBus 的(de)(de)系(xi)統(tong)，設(she)備(bei)之間發(fa)送和接收(shou)消息都是通過 SMBus，而(er)不(bu)是使(shi)(shi)用(yong)單獨的(de)(de)控(kong)(kong)制(zhi)線，這樣可以(yi)節省(sheng)設(she)備(bei)的(de)(de)管腳(jiao)數。 　　使(shi)(shi)用(yong) SMBus，設(she)備(bei)還可以(yi)提(ti)供它的(de)(de)生產信息，告(gao)訴系(xi)統(tong)它的(de)(de)型號(hao)，部件(jian)(jian)(jian)號(hao)等，針對掛起事件(jian)(jian)(jian)保存它的(de)(de)狀態，報告(gao)不(bu)同類別的(de)(de)錯誤(wu)，接收(shou)控(kong)(kong)制(zhi)參數，并返(fan)回它的(de)(de)狀態等。 　　SMBus器(qi)(qi)件(jian)(jian)(jian)存在現有7層(ceng)OSI網絡模型中(zhong)的(de)(de)前3層(ceng)，即(ji)物(wu)理層(ceng)，數據(ju)鏈路層(ceng)和網絡層(ceng)。 　　SMBus最(zui)初的(de)(de)目的(de)(de)是為智能電(dian)池(chi)(chi)，充電(dian)電(dian)池(chi)(chi)和與其他系(xi)統(tong)通信的(de)(de)微控(kong)(kong)制(zhi)器(qi)(qi)之間的(de)(de)通信鏈路而(er)定義(yi)的(de)(de)。SMBus也被用(yong)來連接各種設(she)備(bei)，包括電(dian)源相關設(she)備(bei)，系(xi)統(tong)傳感器(qi)(qi)，EEPROM通訊設(she)備(bei)等等。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范(fan)的全部安全要求，包括3分鐘定(ding)時器(qi)（保護SMBus通(tong)信換效和喚(huan)醒模(mo)式期間鋰(li)離子(zi)電(dian)(dian)池(chi)過充(chong)電(dian)(dian)）。硬件(jian)可編(bian)程(cheng)電(dian)(dian)注和電(dian)(dian)壓限制提供另(ling)外等級保護，這種(zhong)保護由失效軟件(jian)不可能改變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控(kong)制器(qi)，兩個控(kong)制充電(dian)器(qi)參(can)量(liang)的10位DAC，一個熱敏電(dian)阻安全信(xin)號譯碼器(qi)，硬件(jian)電(dian)壓和(he)電(dian)流限(xian)制譯碼器(qi)和(he)一個SMBus控(kong)制器(qi)單元（見圖(tu)1）。

 智能(neng)電(dian)(dian)池或系統控制器通過SMBus接口命令對恒漢(han)和恒壓(ya)(ya)限值進行編程。降壓(ya)(ya)變壓(ya)(ya)器用N-溝MOSFET做(zuo)為開(kai)關，使成本降低(di)、高(gao)效率工(gong)作。熱敏電(dian)(dian)阻安全(quan)檢測電(dian)(dian)路檢測電(dian)(dian)池存在(zai)或確定(ding)電(dian)(dian)池溫(wen)度是否允許安全(quan)充電(dian)(dian)。

當通(tong)過SMBus傳(chuan)輸(shu)(shu)接(jie)收恒(heng)流(liu)(liu)(liu)值時(shi)，它(ta)被(bei)RILIMIT定標和限制到(dao)低于編程值。此修正值編程電(dian)(dian)(dian)流(liu)(liu)(liu)DAC，設置DC充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)。電(dian)(dian)(dian)流(liu)(liu)(liu)DAC是10位△∑DAC，當希望充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)時(shi)，它(ta)從PROG引(yin)腳(jiao)吸收電(dian)(dian)(dian)流(liu)(liu)(liu)（見圖2）。放(fang)大器(qi)PROG引(yin)腳(jiao)吸收電(dian)(dian)(dian)流(liu)(liu)(liu)（見圖2）。放(fang)大器(qi)CAI感測RSENSE上的壓降并使此電(dian)(dian)(dian)壓跨接(jie)到(dao)RS2（200Ω）；流(liu)(liu)(liu)經RS2的電(dian)(dian)(dian)流(liu)(liu)(liu)通(tong)過電(dian)(dian)(dian)流(liu)(liu)(liu)鏡像做為(wei)PROG引(yin)腳(jiao)上的上接(jie)電(dian)(dian)(dian)流(liu)(liu)(liu)。流(liu)(liu)(liu)經RS2電(dian)(dian)(dian)流(liu)(liu)(liu)與來自PROG引(yin)腳(jiao)電(dian)(dian)(dian)流(liu)(liu)(liu)相(xiang)匹配由(you)CA2實現(xian)恒(heng)流(liu)(liu)(liu)工作。由(you)于DAC輸(shu)(shu)出(chu)是一串脈(mo)沖(chong)，所以需要平滑電(dian)(dian)(dian)容器(qi)對(dui)脈(mo)沖(chong)濾(lv)波使其變為(wei)DC。

  LTC1759需要兩個電源(yuan)。PWM電路在墻式(shi)適(shi)配器電源(yuan)斷開時(shi)直接通過Vcc引腳運(yun)行，邏(luo)輯功(gong)能運(yun)行與VDD電源(yuan)無關。PWM電路在去掉(diao)AC電源(yuan)時(shi)能進(jin)入40μA微功(gong)率停機模式(shi)，使邏(luo)輯和SMBus工作(zuo)能保持運(yun)行，這(zhe)是Intel ACPI標準所需要的(de)。這(zhe)種分(fen)離電源(yuan)也使邏(luo)輯和SMBus能根(gen)據系統設計(ji)為員的(de)需要運(yun)行在3V和5V.為使LTC1759邏(luo)輯功(gong)耗最小，邏(luo)輯電流(liu)由時(shi)鐘電路激(ji)勵(li)，時(shi)鐘電路當無動作(zuo)時(shi)停機并蘇醒服務于SMBus動作(zuo)或產生中斷。一旦請求服務，LTC1759便返回到(dao)休眠。

　　當(dang)去掉AC電(dian)(dian)源(yuan)或(huo)去掉電(dian)(dian)池(chi)時，通(tong)(tong)(tong)過CHGEN-SDB引腳(jiao)組合發(fa)生PWM停機。LTC1759通(tong)(tong)(tong)過DCDIV通(tong)(tong)(tong)腳(jiao)檢測AC損(sun)耗。閾值(zhi)通(tong)(tong)(tong)常設置恰(qia)好低于墻(qiang)式適(shi)配的最小(xiao)有(you)效電(dian)(dian)壓。AC電(dian)(dian)源(yuan)狀態通(tong)(tong)(tong)過SMBus可由系(xi)統讀出。UV引腳(jiao)只用于置PWM電(dian)(dian)路進入微功率停機狀態，它直接連到墻(qiang)式適(shi)配器電(dian)(dian)源(yuan)。

　　在設(she)計中電(dian)感(gan)(gan)器選擇不是關鍵，這(zhe)是因為(wei)充電(dian)器的(de)(de)環路響(xiang)應在意地(di)設(she)置很(hen)慢。實際的(de)(de)低限(xian)值為(wei)15μH左(zuo)右，低值電(dian)感(gan)(gan)器將產生較高的(de)(de)紋波(bo)電(dian)流，在輸出需要較低ESR電(dian)容器。

　　輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的選(xuan)擇對ESR（等效(xiao)串聯電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻）不是很(hen)(hen)苛刻，但必須處理來(lai)自充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)的所有(you)紋波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。不用考慮(lv)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的紋波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，因為充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)有(you)效(xiao)阻抗(kang)遠遠大于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感器(qi)(qi)(qi)的ESR。很(hen)(hen)多(duo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)組具(ju)有(you)內部(bu)串聯保護(hu)MOSFET，這提高了(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)ESR。在多(duo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)配置中也有(you)與(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)串聯的功率路由MOSFET，進一(yi)步增加了(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)ESR。從充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)觀點，輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)ESR可高達(da)1Ω，使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)選(xuan)擇范圍(wei)寬。當(dang)采(cai)用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻或電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子負載(zai)時，可能會發生某種不穩定(ding)性(xing)。增加300Ω電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)與(yu)PROG引腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)串聯或在輸(shu)(shu)出(chu)(chu)置10μF電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)能改善穩定(ding)性(xing)。在輸(shu)(shu)出(chu)(chu)不需要用陶瓷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)，因為在很(hen)(hen)輕(qing)負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流聲頻下(xia)開關變換器(qi)(qi)(qi)變得不連接和在下(xia)降周期開始時電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)會造(zao)成噪聲，應該采(cai)用鉭(tan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)。輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)選(xuan)擇由充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)輸(shu)(shu)入(ru)紋波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流（一(yi)般(ban)為最大輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的1/2）決定(ding)。對于4A充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)建議用22μF（50V）陶瓷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)，它(ta)一(yi)般(ban)可處理2A紋波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。

　　從電(dian)池(chi)到墻式(shi)適(shi)配器(qi)的(de)電(dian)流保護由P-溝MOSFET（Q1）提(ti)供。電(dian)壓(ya)比(bi)較器(qi)監控跨(kua)接在MOSFET上的(de)電(dian)壓(ya)而且(qie)當墻式(shi)適(shi)配降到電(dian)池(chi)電(dian)壓(ya)之上小于200mV時關閉MOSFET。盡管價廉(lian)的(de)二極管可用于替代以MOSFET，但(dan)MOSFET只(zhi)增(zeng)加100mV到0.4V低(di)壓(ya)差(cha)工作模式(shi)而不產生額外的(de)熱量。在沒有電(dian)池(chi)起動時間，采用MOSFET附加二極管使墻式(shi)適(shi)配器(qi)電(dian)源能達到Vcc引腳并為PWM控制電(dian)路(lu)供電(dian)。

　　主要的(de)補償是(shi)(shi)d PROG引(yin)腳上進行；然(ran)而DAC脈沖濾波(bo)要求確(que)定(ding)電(dian)(dian)容(rong)器(qi)(qi)有效(xiao)值。脈沖紋波(bo)電(dian)(dian)流(liu)必須小平200mV或環路(lu)起伏（在輕載充電(dian)(dian)電(dian)(dian)流(liu)時(shi)出現的(de)環路(lu)不穩定(ding)性）。Vc引(yin)腳電(dian)(dian)容(rong)器(qi)(qi)的(de)主要功能是(shi)(shi)提供自啟動支(zhi)持。必須有一個1.5K電(dian)(dian)阻器(qi)(qi)與Vc引(yin)腳電(dian)(dian)容(rong)器(qi)(qi)串聯(lian)以(yi)能恰(qia)當停機。

　　從熱觀點考慮，輸出電(dian)(dian)壓在電(dian)(dian)池(chi)(chi)溫(wen)度充電(dian)(dian)范圍(wei)內保持大約0.5%精度。精度越高(gao)，電(dian)(dian)流充電(dian)(dian)容(rong)量就越大，而(er)更(geng)重(zhong)要是在電(dian)(dian)池(chi)(chi)中與電(dian)(dian)壓基充電(dian)(dian)終端(duan)電(dian)(dian)路有(you)關的問題(ti)就會更(geng)少。

　　關于SMBus加速泵，AC適配(pei)電(dian)(dian)流限(xian)制，安全信號感測，安全電(dian)(dian)壓和電(dian)(dian)流范圍設計等問題(ti)在此就不一一詳述。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。